Pallet trucks are often used to lift and maneuver pallets and goods supported thereon during warehousing and shipping. Pallet trucks have been developed to provide varying amounts of functionality to an operator and may be generally categorized as either manual or powered. Manual pallet trucks typically have a frame with forks connected thereto, a truck supported on a pair of rear wheels, and a hydraulic jack connected to the truck and the frame. The jack, which is typically a hydraulic bottle jack, is operated by pivotally pumping a steering handle of the pallet truck up and down which causes the hydraulic bottle jack to raise the frame and the forks thereof off of the ground. Once the pallet has been raised by pumping the handle, an operator may steer the pallet truck by turning the handle relative to the truck. The handle is connected to the hydraulic bottle jack and the pair of rear wheels such that turning the handle generates concurrent turning of the hydraulic bottle jack and the pair of rear wheels. With the pallet raised, the operator pushes or pulls on the handle with sufficient force to maneuver the pallet truck, the pallet, and the goods on the pallet to a desired location. As is apparent, maneuvering the pallet truck, the elevated pallet, and the goods thereon is even more difficult when the pallet truck is positioned on an inclined surface or within relatively tight confines, such as offloading pallets from a semi-truck trailer.
A powered pallet truck has a frame with forks connected thereto, a truck supported on a rear wheel, a hydraulic jack connected to the truck and the frame, and a drive mechanism connected to the rear wheel that assists the operator in maneuvering the pallet truck. Like the manual pallet truck, the powered pallet truck has a handle connected to the hydraulic jack and the rear wheel such that turning of the handle generates concurrent turning of the hydraulic jack and the drive wheel. However, the powered pallet truck has a drive mechanism, such as an electric motor, connected to the rear wheel that allows an operator to propel and brake the pallet truck by way of controls on the handle. This type of pallet truck may be referred to as a semi-powered pallet truck, as the operator still pivotally pumps the handle to activate the hydraulic jack and raise the frame and the forks thereof off the ground. An operator, such as an employee of a local delivery service, may make a large number of deliveries throughout a workday that each involve loading and unloading pallets and the goods thereon. Requiring the operator to manually pump the handle of the pallet truck each time they need to lift a pallet may be ergonomically difficult, particularly when the operator is attempting to move a pallet in limited working areas.
It is therefore desirable in some applications to provide a pallet truck having both a powered drive mechanism and a powered lift mechanism. Prior approaches for this type of pallet truck, which may be referred to as a fully-powered pallet truck, utilize a frame assembly comprising a large front frame having a pair of forks that moves up and down and a large rear frame to which the drive mechanism and lift mechanism are mounted that remains relatively stationary during up and down movement of the front frame. For many prior fully-powered pallet trucks, the drive mechanism comprises an electric drive motor for propelling the pallet truck and the lift mechanism comprises a hydraulic pump and a hydraulic cylinder for moving the front frame up and down relative to the rear frame. By mounting the electric motor, the hydraulic pump, and the hydraulic cylinder to the generally stationary rear frame, wear and tear on the wiring and hoses associated with these components is limited during up and down movement of the front frame and forks thereof. One problem with this type of pallet truck is that the rear frame needs to be relatively large to support the drive mechanism, the lift mechanism, and their associated wiring, hoses, fittings, and the like. Further, because the length of the forks of the pallet truck are generally fixed according to industry standards, providing a sufficiently large rear frame to support the drive mechanism, lift mechanism, and their associated components increases the overall length of the pallet truck and inhibits maneueverability of the pallet truck in tight operating spaces.
Another problem with prior fully-powered pallet trucks is that the configuration of the drive and lift mechanisms adds length to the rear frame and increases the overall length of the pallet truck. More specifically, the drive mechanism of the pallet truck comprises a drive motor mounted vertically or horizontally on the rear frame and the lift mechanism comprises one or more hydraulic cylinders mounted to the rear frame forward of the drive motor that are configured to raise and lower the front frame. Positioning the one or more hydraulic cylinders forward of the drive motor further increases the length of the rear frame which, in turn, increases the overall length of the pallet truck and further inhibits its maneuverability.
Yet another shortcoming with prior fully-powered pallet trucks is that a lower portion of the rear frame needs to be sufficiently strong to support the weight and loading applied by the drive and lift mechanisms. In addition, prior fully-powered pallet trucks have a two-bar linkage between upper portions of the front and rear frames to control relative movement therebetween. The rear frame therefore needs to be sufficiently strong at the lower portion thereof to support the weight and loading applied by the drive and lift mechanisms in addition to being sufficiently strong at the upper portion thereof to support the loading applied to the two bar linkage from the front frame, pallet, and goods on the pallet. This large, strong rear frame is expensive to manufacture, increases the weight of the pallet truck, and decreases the efficiency of the pallet truck due to the increased power necessary to propel the heavier pallet truck.